我试图安装＆＃34; gdal＆＃34;或者＆＃34; PostGIS＆＃34;从自制软件到我的Mac OSX，但我发现了一个错误＆＃34; brew link libpng libtiff proj＆＃34;。
当我尝试＆＃34; brew linklibpng＆＃34;时，我遇到了错误：
Error: Could not symlink share/man/man3/libpng.3
我还尝试过更新＆＃39;，卸载并安装＆＃34; libpng libtiff proj＆＃34;但总有问题：
Error: The `brew link` step did not complete successfully
The formula built, but is not symlinked into /usr/local
Could not symlink share/man/man3/libpng.3
/usr/local/share/man/man3 is not writable.
那里的问题是什么？
$ brew install gdal
$ Error: You must `brew link libpng libtiff proj` before gdal can be installed
$ brew link libpng
Linking /usr/local/Cellar/libpng/1.6.19...
Error: Could not symlink share/man/man3/libpng.3
/usr/local/share/man/man3 is not writable.